The present invention relates to an inexpensive process for preparing glycerol carbonate.
Glycerol carbonate is applied to use in various fields, e.g. raw materials for synthesis of polymers such as polyester, polycarbonate, polyurethane and polyamide, surfactants and lubricating oils. For example, German Patent No. 19756454 discloses application to an emulsifier for cosmetics and a lustering agent. Furthermore it is shown in U.S. Pat. No. 2,856,413 that it can be easily converted to glycidol.
A reaction thereof with phosgene and an exchange reaction with a dialkyl carbonate are known as a conventional method of preparing glycerol carbonate from glycerol. A method of reacting glycerol with carbon monoxide and oxygen at a high pressure in the presence of a catalyst is also known in JP-A 6-157509, corresponding to U.S. Pat. No. 5,359,094. A less expensive, simpler method using a highly safe material, however, has been desired. It has been therefore asked to conduct the reaction with a catalyst easily treated or without catalyst.
The purpose of the present invention is to provide a process for preparing glycerol carbonate simply at a low cost.
The present inventors have found that glycerol carbonate can be synthesized by reaction of glycerol with urea.
The present invention provides a process for preparing glycerol carbonate by reaction of glycerol with urea.
More specifically, the invention provides a process for preparing glycerol carbonate, comprising reacting glycerol with urea in the presence of a metal oxide catalyst or in the absence of any catalyst.
The reaction is preferably carried out in the presence of a dehydrating agent.
It is preferable to feed urea in a 0.2 to 2.0 times as many moles as glycerol.
The reaction may be preferably carried out in the presence of anhydrous magnesium sulfate, anhydrous sodium sulfate, anhydrous calcium sulfate or a molecular sieve.
The catalyst is desirably used in an amount of 0.001 to 10 wt % based on glycerol.
The reaction is preferably conducted at a temperature between 100xc2x0 C. and 140xc2x0 C., more preferably at a temperature between 100xc2x0 C. and 120xc2x0 C., in particular preferably at a temperature between 110xc2x0 C. and 120xc2x0 C.
In the present process comparatively inexpensive glycerol and urea are used as starting materials. Glycerol carbonate can be easily produced just by reacting them with each other. The feeding mole ratio of urea to glycerol may be preferably 0.2 to 2.0, particularly 0.5 to 1.0.
The invention reaction does not essentially need a catalyst. The reaction proceeds smoothly by using as catalyst a metal oxide such as zinc oxide and an alkaline earth metal oxide, e.g. magnesium oxide. A preferred amount of the used catalyst is 0.001 to 10 wt % based on glycerol.
In the present process, it is desirable to use a sufficiently dehydrated glycerol. In the reaction dehydrating agents such as anhydrous magnesium sulfate, anhydrous calcium sulfate, anhydrous sodium sulfate and molecular sieve may be preferably used. The reaction may be conducted preferably in passing of nitrogen gas or at a reduced pressure in order to remove out generated ammonia efficiently. The passing amount of nitrogen gas is not specified as long as ammonia and excess water can be removed. Nitrogen gas may be preferably introduced into the glycerol liquid phase. The reaction may be conducted at a reduced pressure, for example, in the range of 13.3 to 101 kPa.
A preferred reaction temperature ranges from 80xc2x0 to 160xc2x0 C., more preferably from 100xc2x0 to 140xc2x0 C. and particularly preferably from 110xc2x0 to 120xc2x0 C.
According to the present process, comparatively inexpensive materials can be used. No high pressure equipment is not required. Glycerol carbonate can be prepared simply. Glycerol carbonate obtained by the present process can be easily converted to glycidol by known means.